Ball bats, such as baseball and softball bats, are well known. In recent years, metallic bats including a tubular handle portion and a tubular hitting portion have emerged providing improved performance and improved durability over crack-prone wooden bats. The most common tubular bat is the aluminum single-wall tubular bat. Such bats have the advantage of a generally good impact response, meaning that the bat effectively transfers power to a batted ball.
Generally speaking, bat performance is a function of the weight of the bat, the size, and the impact response of the bat. The durability of a bat relates, at least in part, to its ability to resist denting and depends on the strength and stiffness of the tubular bat frame. While recent innovations in bat technology have increased performance and durability, most new bat designs typically improve performance or durability at the expense of the other because of competing design factors. For example, an attempt to increase the durability of the bat often produces an adverse effect on the bat's performance.
The incorporation of these advances and the use of additional materials, such as, other aluminum alloys, titanium alloys and composite materials have resulted in a large variety of well-performing ball bats. Despite such advances in ball bat design and materials, a continuing need exists to further improve the performance, durability and feel of existing bats.
One drawback of recent ball bats formed of aluminum, titanium or composite materials is their cost. Aluminum, titanium and composite materials generally have a high material cost. For example, aluminum can cost up to ten times the price of conventional steel, and titanium is significantly more expensive than aluminum. Further, many metals, such as titanium, are difficult to work with, having very poor workability. Also, the manufacturing costs for composite materials are also relatively high. Still further, the availability of many metals, including titanium, is often variable, making obtaining a consistent supply of material at a generally consistent price difficult. For these reasons, the use of titanium is fairly limited in current bat designs. Aluminum is most commonly used in non-wooden ball bats because of its low material density (lightweight) and its high workability. However, the tensile strength aluminum is generally approximately 85 ksi, which is significantly lower than many other metals. In order to provide sufficient strength and durability, aluminum bats are often formed with a wall thickness as high as 0.110 inches.
Although conventional steel is significantly cheaper and tougher than aluminum or titanium and has relatively high workability, conventional steel is typically not used to form ball bats due to its relatively high weight or density. Further, although conventional steel, after heat treating, has a tensile strength (typically approximately 150 ksi or less), which is greater than aluminum, the wall thickness required to produce a bat formed of conventional steel that is sufficiently durable for competitive play results in a bat that is too heavy for most ball players. Use of heavy materials can negatively affect a player's bat speed and the moment of inertia (“MOI”) of the bat. High quality steels, such as maraging steels, provide a higher tensile strength. However, such high quality steels, are very expensive and difficult to work with, resulting in high material and manufacturing costs.
Thus, a continuing need exists for a ball bat that provides improved performance and high durability at a reasonable cost. It would be advantageous to provide a high performance ball bat that meets all the requirements of conventional play including weight, without excessive material costs or excessive manufacturing costs. What is needed is a ball bat that incorporates and improves on the beneficial material properties and qualities of steel while addressing potentially negative characteristics related to the use of steel, including the weight distribution and MOI of the bat.